1. Field of the Invention
The present invention relates to a method of preparing catalyzed hardware.
2. Description of Related Art
The term catalyzed hardware as used herein relates to catalytic active boiling having the catalyst applied to a metallic surface. Catalysts applied to a metallic surface are advantageous in a number of applications. Coating of catalytic active material on a metal surface is a well known process usually referred to as wash coating and disclosed in the open literature, e.g. Cybulski, A. and Moulijn, J. A., Structured catalysts and reactors, Marcel Dekker, Inc., New York, 1998, Chapter 3, and references herein.
By the known methods, suitable metallic material, preferably a ferritic steel containing Cr and/or Al, is heated to a temperature usually above 800.degree. C. in order to form a surface layer of Cr and/or Al oxide. This layer facilitates proper adhesion of the ceramic material to the steel surface. A thin layer of a slurry containing the ceramic material precursor is applied for on the surface by means of e.g. spraying, painting or dipping. After applying the coat, the slurry is dried and calcined at a temperature usually between 350-700.degree. C. Finally, the ceramic layer is impregnated with the catalytic active material. Alternatively, the catalytic active material is applied for simultaneously with the ceramic precursor.
Certain disadvantages are associated with applying the catalyst to a metal surface by the known methods. Only certain combinations of catalyst and metal can be used since adhesion of the ceramic material to the metallic surface must be obtained. Furthermore, even if adhesion is obtained, the catalyst coating can spall off, since the adhesion strength decreases over due time due to the conditions the catalyst is subjected to. Destruction of the catalytic coating may be caused by thermal stress, dust etc.